Kinetics and Mechanism of Formation of Barium Zirconate from Barium Carbonate and Zirconia Powders

The formation of BaZrO₃ from very fine (70–90 nm) ZrO₂ powders and coarser (∼1 μm) BaCO₃ powders has been studied in dry and humid air up to 1300°C using TGA/DTA, XRD, SEM, TEM, and EDS microanalysis. In the temperature range 900°–1100°C, barium is rapidly transported at the surface of the ZrO₂ particles and reacts, forming BaZrO₃. The compound grows as a concentric layer with gradual consumption of the central ZrO₂ particle. The overall formation kinetics of BaZrO₃ is well described by a diminishing core model, and the most likely rate-determining step is a phase-boundary process at the ZrO₂–BaZrO₃ moving interface. The size and shape of the final particles is generally determined by the morphology of the starting ZrO₂ particles and not by that of the BaCO₃. The reaction is faster in humid air than in dry air, and the activation energy decreases from 294 kJ·mol⁻¹ (dry air) to 220 kJ·mol⁻¹ (humid air). When the fraction reacted is >80–90 mol%, the reaction rate rapidly decreases.     

Ceramic Matrix Composites Life Cycle Testing Under Reusable Launcher Environmental Conditions

This article focuses on the thermal protection system (TPS) and hot structures based on carbon fiber-reinforced SiC (C/SiC) material, which protects the high thermal-loaded areas and control surfaces of a reusable launch vehicle (RLV). The goal of the test program is the evaluation of the lifetime of different types of TPS under reusability aspects for RLV application, reflecting the re-entry environments together with the effect of impacts from low-speed impact, rain erosion, and hail core impact. The test results of the C/SiC samples with the self-healing oxidation protection system showed very promising results concerning reusability and lifetime.     

Age-trend-related differences in tasks involving conjunctive probabilistic reasoning.

Conjunctive probabilistic reasoning has been studied at different ages to ascertain whether the conjunction fallacy is due to a task demand misinterpretation. Such a misinterpretation might occur because a task that requires a comparison between a superordinate class A and a subordinate class A&B is mistakenly interpreted as requiring a comparison between the two complementary subordinate classes of A (i.e., A&B and A¬B). Children (7- and 10-year-olds) and adults were required to make conjunctive probability judgments about problems for which explicit objective probabilities were provided. The total number of A items was kept constant and the frequencies of the A&B and of the A¬B items varied across problems. When the number of A&B items was smaller than the number of A¬B items, the frequency of congruent responses increased with age. When the number of A&B items was greater or equal to that of the A¬B items, the frequency of correct answers decreased. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multistable Circuits for Analog Memories Implementation

In this work two multistable circuits suitable for analog memories implementation will be presented. These circuits have been used to implement completely asynchronous analog memories, one type based on a flash converter and thus having a linear complexity in resolution; the other based on an asynchronous successive approximation converter and thus having a logarithmic complexity in resolution.Experimental results from measurements over prototype chips will be shown and analyzed, and connections with design choiches highlighted.     

Second-order sliding-mode control of container cranes

Moving a suspended load along a pre-specified path is not an easy task when strict specifications on the swing angle and on the transfer time need to be satisfied. Intuitively, minimizing the cycle time and the load swing are conflicting requirements, and their satisfaction requires proper control actions, especially if some uncertainties in the system dynamics are present. In this paper we propose a simple control scheme, based on second-order sliding modes, which guarantees a fast and precise load transfer and the swing suppression during the load movement, despite of model uncertainties and unmodeled dynamic actuators. Such controller has been tested on a laboratory-size model of the crane, and some experimental results are reported.     

Computer generation of colored noise for time-domain analysis of integrated circuits

In many designs it is necessary to establish how noise affects the performance of the circuit under consideration. The type of noise analysis supported by most simulators is a frequency domain small-signal analysis around a DC operating point. This approach cannot be applied to circuits designed to operate in heavily nonlinear conditions. This paper presents an algorithm to generate random time-domain noise signals with a specified power density spectrum. The algorithm can be implemented easily and efficiently in a circuit simulator, and the noise signal thus generated can be used in ordinary transient analysis. Use of this algorithm is demonstrated in the analysis of the noise performance of a comparator and of an optical amplifier.     

Prognosis and immunomorphological characteristics in rectal cancer: results of a multivariate analysis

A new model of 4-alkyl-1-arylpiperazines containing a terminal dihydronaphthalene fragment on the alkyl chain was synthesized in order to have mixed serotonergic and dopaminergic activity and to pursue the recent alternative approaches to the discovery of novel antipsychotic and anxiolytic agents. Title compounds were evaluated for in vitro activity on dopamine D-2 and serotonin 5-HT1A and 5-HT2 receptors by radioreceptor binding assays. They show high nanomolar affinity for 5-HT1A, moderate affinity for D-2, and low affinity for 5-HT2 receptors, and in particular, two compounds, 4-[3-(1,2-dihydro-6-methoxynaphthalen-4-yl)-n-propyl]-1-(2- methoxyphenyl)piperazine (8) and 4-[3-(1,2-dihydro-8-methoxynaphthalen-4-yl)-n-propyl]-1-(2- pyridyl)piperazine (15), show values (nM) of IC50 = 2.0 and 1.4 for 5-HT1A and IC50 = 90.6 and 119.3 for D-2, respectively. Some in vivo behavioral studies show compound 8 to be an antagonist on 5-HT1A receptors. These first findings place the new arylpiperazines on the same level as that of the azaspirone class, e.g., 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)-n-butyl]piperazine (NAN-190) and buspirone.     

A Textile Dressing for Temporal and Dosage Controlled Drug Delivery

Chronic wounds do not heal in an orderly fashion in part due to the lack of timely release of biological factors essential for healing. Topical administration of various therapeutic factors at different stages is shown to enhance the healing rate of chronic wounds. Developing a wound dressing that can deliver biomolecules with a predetermined spatial and temporal pattern would be beneficial for effective treatment of chronic wounds. Here, an actively controlled wound dressing is fabricated using composite fibers with a core electrical heater covered by a layer of hydrogel containing thermoresponsive drug carriers. The fibers are loaded with different drugs and biological factors and are then assembled using textile processes to create a flexible and wearable wound dressing. These fibers can be individually addressed to enable on‐demand release of different drugs with a controlled temporal profile. Here, the effectiveness of the engineered dressing for on‐demand release of antibiotics and vascular endothelial growth factor (VEGF) is demonstrated for eliminating bacterial infection and inducing angiogenesis in vitro. The effectiveness of the VEGF release on improving healing rate is also demonstrated in a murine model of diabetic wounds.